1. Field of the Invention
THIS INVENTION relates to microtomes, that is to say to devices used for cutting thin sections from specimens for, for example, microscopic examination. The invention relates, more particularly, to microtomes which are to some degree mechanised or automatic in operation.
2. Description of Related Art
Mechanised or automatic microtomes are known which comprise a rigid base, a knife holder secured to said base, a microtome knife secured in the knife holder and a specimen support, on which a specimen to be sectioned is mounted, the specimen support being mounted for movement relative to the base so as to cause a specimen mounted on the specimen support to execute a transverse movement with respect to the knife blade, appropriate to the cutting of slices or sections from the specimen. Generally, in such known microtomes, the specimen support is also mounted for advancing and retracting movement relative to the knife for the cutting of successive sections or slices from the specimen and for withdrawing the specimen holder from the region of the knife for mounting a fresh specimen and so on.
In known microtomes of this character, the microtome knife is supported in a knife holder which is adjustable in position to vary the proximity of the knife to the specimen holder. This known arrangement has, however, the disadvantage that the knife is not always supported as rigidly as it might be, with consequent deficiencies in the operation of the microtome.
It is an object of the invention in one of its aspects to provide an improved microtome in which the firmness of mounting of the microtome knife can more readily be assured than in the past.
According to this aspect of the invention there is provided a microtome comprising a base, a knife-holder mounted on the base for supporting a microtome knife, a specimen holder mounted for longitudinal movement relative to the base towards and away from the knife-holder and also mounted for transverse movement relative to the knife holder for displacing a specimen held by the specimen holder relative to a knife mounted in the knife holder for cutting sections from such specimen, wherein the knife holder is mounted directly on the base without provision for adjustment of the position of the knife holder on the base such as to vary the location of the knife edge in relation to said edge.
In addition to the rigidity secured in accordance with this aspect of the invention, the fixed knife mounting, in the preferred embodiment makes for ease of cleaning the instrument.
The invention in another of its aspects provides improved means for ensuring reproducibility of the microtome knife angle with respect to the specimen to be sectioned, between replacements or other adjustments of the knife relative to the remainder of the microtome. It is known that, in operation of mechanised or automatic microtomes, in particular, different angles are required for the various plates or knives used to compensate for different facet angles, embedding mediums and materials to be sectioned. Routine practice requires the setting of only one angle on the knife holder, which angle can be maintained or reproduced when, for example, the knife holder is removed for cleaning or replaced with an alternative holder. In conventional microtomes, it is normal to utilize a knife holder having a base which is removable from the frame or base structure of the microtome and which is replaceable on such structure. Accordingly, in normal practice, the knife holder and its base are removed together from the remainder of the machine and replaced together, so that the knife angle is thereby retained. In a microtome in accordance with the first aspect of the invention, where the knife holder, or at least the knife holder base, is a fixed part of the base or frame of the microtome as a whole, the procedure described above in relation to conventional microtomes is not available and it is an object of the present invention, in another of its aspects, to provide a means of maintaining or reproducing a predetermined angle of the microtome knife when mounted in the microtome, which means is not confined to microtomes having knife holders with bases removable from the remainder of the microtome with the knife holder.
In accordance with this further aspect of the invention, accordingly, there is provided a microtome comprising a knife holder and a knife holder support having cooperating arcuate bearing surfaces permitting angular movement of the knife holder relative to the knife holder support about the axis of curvature of said bearing surfaces with concomitant sliding movement of one of said arcuate surfaces over the other, wherein a sensor or locating device is adjustably secured to the component providing one of these bearing surfaces, for cooperation with a datum provided on the component providing the other of these arcuate bearing surfaces, to ensure that with said sensor or locating device fixed to said component providing said one of said bearing surfaces the angular position of the knife holder on the knife holder support at which said sensor or locating device cooperates with said datum can readily be established.
The invention in another of its aspects relates to the mounting of the specimen holder in a microtome. In microtomes in which the specimen holder is advanced towards and is retractable from the knife, it is important, for proper sectioning of the specimen, that the specimen support, whilst being adjustable in position relative to the remainder of the microtome structure, be supported rigidly in such a way as to resist effectively any unintended displacements and deflections. This is particularly so in the case of the microtome in accordance with the first-noted aspect of the invention in which the position of the microtome blade is fixed and in which the specimen holder must therefore be capable of being advanced over a greater linear range towards and away from the blade than in microtomes in which there is the possibility of mounting the blade holder nearer to or further from the structure for which the specimen support is supported.
According to this aspect of the invention, accordingly, there is provided a microtome comprising a base, a knife-holder mounted on the base for supporting a microtome knife and a specimen holder mounted for longitudinal movement relative to the base towards and away from the knife holder, wherein said specimen holder comprises a slide mounted for longitudinal movement in a bearing arrangement including first and second bearing elements at longitudinally spaced positions along the slide, and limiting transverse movement of the slide in one direction and a third bearing element at a longitudinal position intermediate the first-mentioned longitudinally spaced positions and biased towards the slide so as to urge the latter into engagement with said first and second bearing elements.
The features according to this aspect of the invention are of particular utility in relation to a microtome in accordance with the first aspect of the invention, where the fixed knife position requires the specimen to be moved up to the knife rather than vice versa. To allow for a range of block depths or of specimen depths to be sectioned, enough specimen travel must be allowed between specimen and knife position. This implies that the specimen may be required to be sectioned with the specimen holder supporting the specimen at or near to its full extension from the structure from which the specimen holder is adjustably supported, so that the need for stable support of the specimen holder is particularly acute.
According to a yet further aspect of the invention, there is provided a microtome comprising a base, a knife fixed with respect to the base, a specimen holder mounted for longitudinal movement relative to the base towards and away from the knife, motor means for advancing and withdrawing the specimen holder automatically to controllable extents, and automatic control means capable of advancing or retracting the specimen holder to a pre-set position upon execution of a command operation.
This feature enables the rapid positioning of the specimen from the loading/unloading position to the trimming/sectioning position. In microtomes in accordance with the first-noted aspect of the invention, in particular, the fixed knife position means that the specimen must always move up to and away from the knife, rather than vice versa and the auto-load feature speeds up the processing between blocks or specimens when the correct xe2x80x9cmemoryxe2x80x9d position is set and ideally ensures no clashes between block and knife.